Potassium Carbonate → 2-(1', 2'-dihydro-2'-oxospiro[cyclopentane-1,3'-[3H]indol]-5'-yl)-1H pyrrole-1-carboxylic acid, tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

5-(2′-Oxo-2′,3′-dihydrospiro[cyclopentane-1,3′-[3H]indol]-5′-yl-2-cyanopyrrole: A solution of 5′-bromospiro[cyclopentane-1,3′-[3H]indol]-2′(1′H)-one (2.0 g, 7.5 mmol) and tetrakis(triphenylphosphine)palladium(0) (430 mg, 0.3 mmol) in ethylene glycol dimethyl ether (50 mL) was stirred under a flow of nitrogen for 15 min. To the solution was added sequentially 1-t-butoxycarbonylpyrrole-2-boronic acid (2.1 g, 9.7 mmol) and potassium carbonate (2.4 g, 17 mmol) in water (10 mL). The mixture was heated to 80° C. for 3 h and allowed to cool. The reaction mixture was poured into water (50 mL) and extracted with ethyl acetate (3×50 mL). The organic layers were combined, washed with brine (30 mL) and dried over magnesium sulfate. The solution was filtered and concentrated in vacuo. Crystallization from 20% ethyl acetate/hexane gave 2-(1′,2′-dihydro-2′-oxospiro[cyclopentane-1,3′-[3H]indol]-5′-yl)-1H-pyrrole-1-carboxylic acid, tert-butyl ester (2.2 g, 83%) as a white powder, mp 179–180.5° C. 1H NMR (DMSO-d6, 400 MHz) δ 1.30 (s, 9H), 1.75–1.98 (m, 8H), 6.16 (dd, 1H, J=1.8, 3.3 Hz), 6.22 (‘t’, 1 H, J=3.3, 3.3 Hz), 6.79 (d, 1 H, J=7.9 Hz), 7.08 (dd, 1 H, J=1.8, 7.9 Hz), 7.14 (‘d’, 1 H, J=1.5 Hz), 7.28 (dd, J=1.9, 3.3 Hz), 10.30 (s, 1 H). MS (EI) m/z 352 [M+]. Anal. Calcd for C21H24N2O3: C, 71.57; H, 6.86; N, 7.95. Found: C, 71.08; H, 6.83; N, 7.74.

Provenance & Evidence